AJAX implements the user name detection function without refreshing, and ajax refresh detects the user name

AJAX implements the user name detection function without refreshing, and ajax refresh detects the user name

Let's take a look at the schematic diagram.

Register. php

<! DOCTYPE html> 
RegisterPro1.php
<? Php // return data (text, xml, json) to the ajax engine (line 3 http Response) // header ("Content-Type: text/xml; charset = UTF-8 "); // tell the browser that the returned header is in xml format (" Content-Type: text/html; charset = UTF-8 "); // tell the browser, the returned result is in text/json format $ username = $ _ POST ["username"]; // ① // if ($ username = "abc ") {// echo 'network name unavailable '; //} else {// echo 'network name available'; //} // ② // $ info = ""; // if ($ username = "abc") {// $ info. = "<res> <mes> network name unavailable </mes> </res>"; //} else {// $ info. = "<r Es> <mes> available network names </mes> </res> "; //} // echo $ info; // ③ // $ info = ""; // if ($ username = "abc") {// $ info returns a string // $ info. = '{"res": "unavailable", "id": "123", "age": "5"}'; //} else {// $ info. = '{"res": "available", "id": "3", "age": "1"}'; //} // echo $ info; // ③ + $ info = ""; if ($ username = "abc") {// here $ info returns a string $ info. = '[{"res": "unavailable", "id": "123", "age": "5" },{ "res ": "abc unavailable", "id": "3", "age": "0"}] ';} else {$ info. = '[{"res": "available", "id": "1 ", "Age": "15" },{ "res": "available", "id": "83", "age": "9"}] ';} echo $ info;?>
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